Lapping machine



July 19, 1960 1.. J. LA BARRE ETAL 2,945,331

LAPPING momma Filed ma 16, 1957 3 Sheets-Sheet 1 'INVENTORS Lawrence JLa flan-e A TTORNE Y:

' LAPPING MACHINE Filed May 16, 1957 3 Sheets-Sheet 2 FIEJ E INVENTORSlawns/7C6 J La fiarre BY M/i/l/am Girdner ATTORNEYS 1960 L. J. LA BARREETAL I LAPPING MACHINE Filed'uay 7 3 Sheets-Sheet 3 LAPPING -MAGHINELawrence J. La Barre, Mountain, View, and'William I.

Girdner, Mcnlo Park, Calif, assignors to Hewlett- Packard Company, PaloAlto, Calif, a corporation of California Filed May 16, 1957, Ser. No.659,513

4 Claims. 01. 51-131 This invention relates generally to lappingmachines.

'It is a general object of the present invention to provide an improvedlapping machine into which the Work may be rapidly inserted and removedfor grinding and surfacing on a mass production basis, and in which thelap surface is continuously conditioned during the lapping operation.

Another object of the present invention is to provide a lapping machinein which a conditioning ring extends over the edges of the lap and inwhich the pressure hetween-the conditioning ring and the lap may becontrolled to condition the lap as desired while the work is beingoperated upon.

It is another object of the present invention to provide a lappingmachine in which the lap surface is continuously in contact with aconditioning ring which extends over the edges of the lap and whichincludes means for controllably applying pressure to the ring wherebythe pressure at the inner or outer edges of the lap surface may beincreased as desired to control the shape of the lap surface.

It is another object of the present invention to provide a lappingmachine in which the lap surface is continuous- 1y conditioned by aconditioning ring rotatably mounted on its axis and in which means areprovided for coutrolling the pressure between the conditioning ring andthe inner and outer edges of the lap surface whereby the lap surface maybe conditioned to be .plane, concave for convexas desired.

It is still another object of the present invention to ."p oyi-de alapping machine in which a plurality of work j holders are pivotallymounted and spaced from the lap surface and which include means forcontrolling the spacingo'f thework holders from the lap surface.

These and other objects of the invention will become more clearlyapparent from the following description taken in conjunction with theaccompanying drawing.

Referring to the drawing:

Figure l is a top plan view of a lapping machine in accordance with theinvention;

Figure 2 is a side elevational view partly in section takenalong theline 2-2 of Figure 1;

Figure 3 is an enlarged view taken along the line 3-3 of Figure .1 andshowing the work holder stem locking and positioning means;

Figure 4 is an enlarged view of the stern locking means taken along theline 4-4. of Figure 3;

' Figure 5 is an enlarged sectional view taken along the line 5-5 ofFigure 1 showing the rotatable wear ring and the means for controllingthe pressure between the wear ring and the inner and outer surfaces ofthe lap;-

Figure 6 is an enlargedview of the pivotal mount for 7 the wearring; and

Figure-7 is an enlarged-view showing the lower end of the work holderstem, the bearings associated therewith :aud-iheworkholder; g e

:A supporting gfii'ame designatedz generally by the refer- Patented July19, 1960 'the legs 12. Reinforcingchannels 14 are disposed at the upperend of the legs and serve tosupport the lap, as will be presentlydescribed. A plate 16 extends across the apparatus and rests on a pairof the members 13. The plate 16 serves to support an electric motor 17and the gear reduction box 18. A suitable pulley 19, for example, adouble groove V-belt pulley, receives the V- belts 21. The belts engagethe pulley 22 which is attached to the'turntable shaft. The .pulley 22is suitably attached to the lower end of the shaft 23 as, for example,by the collar 24 and set screws 26.

The turntable, work holders and related parts are carried by the angleirons 2.7 and 28 which extend trans versely across the framework and aresupported by the channels 14. The aforementioned parts are supported bysuitably securing the shaft housing 29 to the angles 27 and 28. Forexample, the housing 29 may extend through a plate 32 and be suitablywelded thereto. Bolts 33 serve to secure the plate to the angles 27 and28. The turntable shaft 23 extends downward into the housing 2.9 and isengaged by the inner race of the upper and lower bearings 34, 36 whichare carried within the housing. The spacer 37 serves to hold thebearings in spaced relationship. The lower bearing is provided with asuit able seal 38. A thrust bearing 39 has an upper race 'which issecured to the shaft 23. The lower race is engaged in the annular recess41 formed in the upper end of the housing 29. A gasket 42 and a dripring 43 are interposed between the shoulder 44 formed on the shaft andthe upper race of the bearing 39.

The turntable 46 is received by the upper end of the shaft (Figures 2and 5) and rests on the shoulder 44 formed on the shaft. The shaft isthreaded at 47 to receive the lock nut 48 which serves to secure theturntable to the shaft. A suitable driving pin 49 is secured to theshaft and extends through the slot 51 formed in the table hub.

The turntable comprises an upper lapping surface 52 which is providedwith a plurality of radial grooves 53 alternate ones of which extendcompletely across the lap ping surface. The grooves act in conjunctionwith the work and conditioning ring, to be presently described, tomaintain the surface of the lap clean. The grooves are deeper at theouter edge of the lap surface whereby the oil and grit tends to flowoutwardly and into a collecting trough to be presently described.Referring particularly to Figure 2, the grooves 53 are shown extendingfrom the inner edge of the lapping surface outwardly and downwardly tothe outer edge. A plurality of web-like reinforcing members 54 extendbetween the hub of the turntable and the lower edge of the table andserve to reinforce the same.

The oil and grit which flow outwardly from the lapping surface dripsdown the outer edge of the table into the trough 56. The trough 56 hasan outer edge which extends upwardly a short distance above the loweredge of the turntable and an inner edge which extends upwardly and isspaced from the lower edge of the turntable. To prevent the migration orflow of oil inwardly along the lower surface-of the turntable, a pairofgrooves 57 are formed in the lower side near the periphery of theinternal diameter which serves to accommodate the bear- "ings 67 and 68which are held in spaced relationship by the spacer 69. The lowerbearing 68 has its inner race abutting against the shoulder formedbetween the threaded portion 47 of the shaft 23 and the upper-portion.Work holder arms 71 are suitably secured to the assembly designatedgenerally by the reference numeral 72. The arms '71 may, for example, besecured thereto by means of bolts 73. a

Referring particularly to Figure 5, the details of the assembly 72. arefully illustrated. The assembly'comprises an anchor sleeve 74 which isadapted to slide over the pivot column and to be secured thereto as, forexample, by means of the set screws 76 which ride into accommodatingindentations formed on the column. The upper portion of the sleeve isthreaded to receive the anchor sleeve nut 77. The anchor sleeve nutprovides an adjustment for the vertical height of the work holder hub79. The work holder hub- 79 has an eccentric recess 81 formed in itsupper end. A lock ring 82 having an eccentric portion adapted to fitinto the recess fits over the hub. Upon turning movement of the ring bymeans of a spanner wrench which engages the holes 83, the members 79 and82 are locked to the pivot column 66.

The work which is operated upon by the surface of .the lap is held in aplurality of work holders 86 illustrated in Figures 1, 2 and 7. The workholders comprise plates having work receiving openings therein intowhich the work 87 is placed, as illustrated in Figure 7. The bottomsurface of the work is frictionally engaged by the lap surface andground to a true surface. As will be presently described, means areprovided for spacing the work holder above the surface of the lap wherethey do not wear the lap. Each of the work holders is rotatably mountedon a vertical shaft or stem which is suitably engaged by one of the arms7&1. The arms and stem prevent the work holder from rotating with thelap. As is apparent, the'work which is operated upon by the outerperiphery of the lap is in contact with a portion of the lap which istraveling at a greater velocity than the inner surface. As a result, atorque is developed which rotates the work holder. Thus, each piece ofwork is operated upon by various portions of the lap surface. Further,as will be presently described, the work itself serves to condition ordress the lap.

The work holder mount (Figure 7) may, for example, include a bearingholder 88 which is press fit to the shaft or stem 89 and which serves tohold the bearings 91 and 92. A short shaft 93 has its upper end pressfit into the inner race of the bearings and its lower end press fit intothe head 94. The head comprises a pair of cylinder-like members whichare interconnected at the top. The lower outer edge of the outercylindrical memberis provided with a circumferential notch 96 whichserves'toreceive the work holder disc 86. The outer cylinder islongitudinally slotted. A plurality of set screws 97 which bear againstthe inner cylinder serve to urge the outer cylinder outwardlyto firmlyhold the disc 86 in the groove 96.

The stem 89 extends upwardly through the holding arms 71 shown in detailin Figures 2 and 3. The shaft is locked in a vertical position by meansof a stern lock 98 which includes cutout 99. The stem lock is insertedin an accommodating hole formed in the arm 71. A nut 101 engages thethreaded outer end of the stem lock. Upon turning movement of the nut101, the cutout portion of the stem lock is cammed against the shaft 89and s r c he s me.- i

Means are provided for accurately positioning the work holder above thelapping surface. A hub 102 provided with an eccentric opening 104 servesto receive an eccentric nut 103 to form a stem lock. By turningmovements of the nut and hub with respect to one another, the stem lockis locked to the shaft; A raised disc 107 is mounted on the arm 71 bymeans of the bolt 108. The disc 107 has a varying thickness whereby thesame may be rotated to urge the stem lock upwardly to lift the stem. In

operation, the work holding disc is placed on the lap surface and thestem lock is locked. The disc is then rotated to lift the stem apredetermined amount corresponding to the height of the incline of thedisc. The stem lock nut is then rotated and the stem is locked to thearm. In this manner the work holding disc is'spaced a suitablepredetermined distance from the surface of the lap. The pivot column 66,arms 71 and the holders are prevented from turning with the lap by thebar 109 which engages the post 110. The post 110 is secured to theframe.

Thus, it is seen that a work holder arrangement is provided in which thework holder may be accurately spaced from the lap surface and in whichthe work holder is free to rotate about its axis.

As is well known, as the work is operated upon by the lapping surface,there is a tendency for the lapping surface to become uneven. In manytypes of lapping machines, the work is removed after a predeterminedperiod of operation and the surface of the lap is dressed orconditioned. In the present machine, asuitable wear ring continuouslyengages the surface of the lap. The wear ring is of such a weight andproportions and is so arranged that it continuously conditions the lapsurface as the work is being operated upon.

Referring now more specifically to Figures 1, 2 and 5, the conditioningarrangement is illustrated. A relatively heavy conditioning ring 111 hasits lower edge provided with a plurality of radial slots 112. The ringis of such dimensions that it overhangs the inner edge 113 and the outeredge 114 of the lap surface. The conditioning means is in the form of aring and suitable mounting means, for example, a mounting plate or cover116 is suitably secured thereto. A bearing holder 117 is secured ito theplate and accommodates the bearings 118 and 119. The conditioning ringstem 121 extends into the bearings.

The stem is provided with an elongated slot 122 which serves to'accommodate a pin 123 whereby the stem is pivotally held by the pin. Thepin 123 is suitably secured to the fork of the inwardly extending arm124, as for example, by bolts 126. The arm 124 is suitably mounted to achannel 127 (Figure 1) which extends downwardly and is secured to theframe 11. The arm 124 prevents the conditioning ring from rotating withthe lap. The upper portion of the stern 121 is provided with a threadedportion of reduced diameter. A weight bar 128 fits over this portion andthe nut 129 serves to secure the same to the stem 121. The bar providesmeans for controlling the pressure between the inner or outer edges ofthe lap surface and the conditioning ring. Weights are placed on theweight bar to control the pressure between the wear ring and the innerand outer surfaces of the lap. When a weight is placed on the bar towardthe center 'of the lapping machine, the pressure between the Wear ringand. the lap surface at the inner edge of the lap is increased. Theinner edge of the lap is worn more than the outer edge and the lapbecomes concave. Similarly, if the weight is placed on the bar towardthe outside of the machine, the outer edge wears to greater extent thanplane or flat by properly positioning the weight on the weight bar.

A work holder 141 of the type previously described is rotatably mountedon the shaft 121 by meansof bear- Simple and efilcient means is ings(not shown). The work holder has an outside diameter which is less thanthe inside diameter of the wear ring whereby it may rotate independentlyof the same. Means (not shown) is provided for positioning and holdingthe work holder above the lap surface whereby it rotates free of thesame.

Additional work holders 144 are rotatably supported by a shaft 145 whichextends upwardly and is engaged by the arm 146. The arm and work holderare supported by a vertical member which is secured to the frame 12.These work holders are disposed in the open portions of the lap whichexist between the relatively large work holders, previously described,and between the large work holders and the wear ring. It is apparentthat additional work holders may be employed since the larger workholders and the wear ring are held at a fixed radial distance from thecenter of the lap.

The addition of the smaller work holders 144 and the work holder 141disposed in the work ring, increases considerably the surface area ofthe lap which is employed.

A tank 131 holds the oil and grit. The tank is supported by the plates132 which are suitably attached to the frame and extend upwardlytherefrom. The motor 133 drives the agitator 134 through the speedreduction gear 136. The oil and grit are fed from the tank onto thelapping surface along the wire 1137.

Operation of the lap is as follows. The work holders are positionedabout the surface of the lap as previously described. The work is placedin the work receiving openings of the work holders as illustrated inFigure 7 wherein a number of wave guide sections 87 are shown in place.The turntable is rotated to produce relative movement between the lapsurface and the work pieces. Oil and grit are continuously supplied tothe surface. As privously described, the oil and grid flow outwardlyalong the grooves 53 into the trough 56. Rotation of the lap inducesrotation of the work holders and work whereby the same come into contactwith different portions of the lap as the lapping operation progresses.This turning movement of the work holders and work aids in maintainingthe lap surface in condition.

Any unevenness of the lap surface is corrected for by the conditioningring 111 which is rotatably mounted and which has its work surface incontact with the surface of the lap. As previously described, theconditioning ring stem 121 is pivotally mounted. A weight bar is securedto the upper end of the stem and provides means for controlling thepressure between the work surface of the wear ring and the lap surface.Thus, during operation a weight is placed on the weight bar and is movedradially, inwardly and outwardly, as desired, to maintain the surface ofthe lap concave, convex or flat. It has been found that once the weightis properly positioned the lap may be operated for many hours withoutreadjustment of the position of the weight.

Thus, it is seen that we have provided an improved lapping machine inwhich the work holders do not cause wear of the lap surface since theyare spaced therefrom. provided for conditioning the surface. We haveprovided a convenient means for controlling the lapping surface withoutchanging the position of the work or conditioning ring. Said meansconsists of a weight bar which serves to control the pressure betweenthe conditioning ring and the inner and outer edges of the annular lapsurface. Further, we have provided a means for making a great percentageof surface of the lap available for work.

We claim:

1. A lapping machine comprising a frame-like structure, a turntablerotatably mounted on said frame-like structure and having an annularlapping surface, means for driving said turntable, work holding meansspaced from the surface of said table and including work receivingopenings, means for rotatably mounting said work holding means, meanspreventing movement of the work holding means with the turntable, aconditioning ring extending over the inner and outer edges of saidsurface, means for rotatably mounting said conditioning ring, saidmounting means including a stem, means pivotally mounting said stem, anda weight bar carried by the other end of said stem and adapted toreceive weights which urge the stem to pivot about the pivotal mountingmeans to thereby control the pressure between the inner and outer edgesof said surface andthe conditioning ring.

2. A lapping machine comprising an annular lap, means serving to rotatesaid lap, work holding means, a conditioning ring extending over theinner and outer edges of said annular lap, means for rotatably mountingsaid conditioning ring, said mounting means including a stem, a slotformed in said stem, a pin pivotally engaging said stem through saidslot, an inwardly extending arm having the pin aflixed thereto andpreventing movement of the conditioning ring with the lap, and a weightbar carried by the upper end of said stem and adapted to receive weightsto thereby tend to pivot the stem about the pin to thereby control thepressure between the inner and outer edges of the lap and theconditioning ring.

3. A lapping machine comprising a frame-like structure, a vertical shaftrotatably mounted in bearings carried by said frame, a turntable carriedby said shaft, means for driving said shaft and turntable, a pivotcolumn mounted at the upper end of said shaft and extending upwardly,work holding arms mounted to said column and extending radially outward,work holding means spaced from the surface of said table and includingwork receiving openings, means serving to rotatably mount said workholding means, stems extending upwardly from said rotatable mountingmeans and through said arms, said arms including means for locking thework holding stems in a predetermined vertical position, means foraccurately positioning said stems in a vertical direction, aconditioning ring extending over the inner and outer edges of theturntable, means for rotatably mounting said conditioning ring, saidmounting means including a stem, means pivotally engaging said stem, anda weight bar carried by the upper end of said stem and adapted toreceive weights to urge the stem to rotate about the pivot to therebycontrol the pressure between the conditioning ring and the inner andouter edges of said turntable.

4. A lapping machine comprising an annular lap, means serving to rotatesaid lap, work holding means, a conditioning ring extending over theinner and outer edges of said annular lap, means for rotatably mountingsaid conditioning ring, said mounting means including a stem, a slotformed in said stem, a pin pivotally engaging 'said stem through saidslot, an inwardly extending arm having the pin fixed thereto andpreventing movement of the conditioning ring with the lap, a weight barcarried by the upper end of said stem and adapted to receive weights tothereby tend to pivot the stem about the pin to thereby control thepressure between the inner and outer edges of the lap and conditioningring, and a work holder rotatably carried at the other end of said stem,said work holder having a diameter which is less than the insidediameter of the conditioning n'ng whereby the same is free to rotateindependently thereof and disposed above the lap surface whereby itrotates free of the same.

References Cited in the file of this patent UNITED STATES PATENTS1,763,647 Danner June 17, 1930 2,079,076 Kranich May 4, 1937 2,541,912Broughton Feb. 13, 1951 2,597,382 Roshong May 20, 1952 2,607,173Garrison Aug. 19, 1952 2,772,521 Voytech Dec. 4, 1956 2,782,571 HansonFeb. 26, 1957

